Not necessarily the oil pump causing that, it could be the breather valves in the heads or over filled oil tank level.

It's common on the sportsters and softails because the oil tank is higher than the engine. You may try some marvel mystery oil in the engine oil and run it for a few hundred miles and change the oil and filter. It could be just a bit of sediment causing the problem in the check valve.

Being an evo motor, it could also be the breather unit in the nose cone either damaged like a lot of them were or out of timing because of a bad gear on the breather unit itself. It's timed with a gear to the crank and cam and when it is out of time from a damaged gear it opens at the improper time and builds pressure in the crank which then relieves itself from the breather.